The present invention relates to an improved cylinder-operated driving mechanism for a ball valve, mainly consisting of a cylinder with an air guide passage, pistons, a driving shaft seat, a driving shaft, links, and a plurality of compression springs, and being characterized by that, when the cylinder has not air supplied to it, the compression springs may, by the compressed spring force stored therein, automatically push the two horizontally opposite pistons in the cylinder to turn the driving shaft and thereby cause the ball valve connected thereto to close. That is, the ball valve can be automatically closed without the need of any externally exerted force.
The ball valve is widely applied in industrial fields, and the most ideal control manner of a ball valve is to use a cylinder-operated driving mechanism connected with the ball valve. FIG. 4 illustrates a conventional cylinder-operated driving mechanism for a ball valve, in which two air passage systems are required. One of the air passage systems mainly includes a first air supply passage inlet 14 and is used to open the ball valve; the other one mainly includes a second air supply passage inlet 15 and is used to close the ball valve. These two air supply passage systems alternately open and close to drive pistons 2 in the cylinder 1. To close the ball valve, air is discharged from a cylinder chamber 111 of the cylinder 1 via the first air supply passage inlet 14, and another air flow is supplied to the cylinder 1 via the second air supply passage inlet 15 and flows through an air passage 151 communicable with the inlet 15. The in-flow air forces the two pistons 2 in the cylinder 1 to move toward each other and thereby causes two links 4 connecting the pistons 2 to a driving shaft seat 3 on a driving shaft 5 to drive the driving shaft 5 to turn in a reverse direction. Since the driving shaft 5 connects with a control stem of the ball valve, the turning of the driving shaft 5 in the reverse direction shall cause the ball valve to close.
In such a ball valve driving mechanism with two air supply passage systems, high cost and high reliability of the equipment is required, because any unexpected stop or failure of the air supply passage system for closing the ball valve during the whole operating course will disable the entire clyinder-operated driving mechanism and the ball valve controlled by the latter shall keep open without being timely closed which will cause unimaginable result. Therefore, it is desirable to improve the conventional cylinder-operated driving mechanism for ball valves to overcome the above shortcomings and to obtain better efficiency in practical use.